Field of the Invention
The invention relates to an electronic component and the utilization of a guard structure contained in the component to guard against electrostatic discharge. In the past, electronic components have customarily been provided inside a housing, with feeders (contacts) leading out for delivering the energy supply and feeding signals in and/or out. Among these electronic components, those components containing a CMOS semiconductor chip in the housing interior are very sensitive to electrostatic discharge. Potential differences acting on the component from the outside cause charge transfers, which can ultimately lead to an overvoltage at one or more of the gate capacitors, causing a direct discharge between the individual plates of the gate capacitors, which usually destroys the component. This kind of electrostatic charge which destructively discharges can be caused by physical contact; therefore, steps are taken in electronics laboratories to protect against it, for instance by bearing the components on a piece of conductive microcellular rubber. Furthermore, people who come in contact with the components in electronics labs frequently wear corresponding grounding straps, so that contact does not produce a charge. Appropriate precautions are taken for production by use of surface mounting apparatuses, in which the components are mounted on printed circuit boards (PCBs).
If the components are first built into a circuit, there remains a slight danger that the component may be destroyed by electrostatic discharge. But this can occur at any time due to circuit errors or defects of other components. To avoid this, electronic components typically contain additional protective structures to protect against electrostatic discharges (ESD protection) as well as overvoltages that are fed in. They are usually circuits that dissipate overvoltages.
A fundamental disadvantage of such an ESD protection is that it xe2x80x9ccosts chip space,xe2x80x9d which contributes nothing to the actual functionality of the electronic component. Another disadvantage of ESD protection is that it frequently changes the functionality of the component. The ESD protection frequently adversely affects the sensitivity and/or dynamic of the component. New electronic components today do not contain a closed housing, so that parts of the semiconductor chips are exposed to the outside. The new electronic components include what are known as chip sizes packages (CSP), in which the chip is assembled with its contacts directly on a printed circuit board. Furthermore, various sensors are also increasingly being produced as semiconductors. Both in CSP and when used as a sensor, the component as a whole, or at least a proportionally relatively large area, is freely accessible to the environment.
These instances reinforce the need for protective measures against electrostatic discharge. Such components also include fingerprint sensors, which contain a matrix of several individual capacitors. It is provided that the finger from which a print is to be taken touches the component directly. Particularly in such a case, a static charge can easily occur, since in the normal use of such a sensor it is unacceptable if the finger has to be grounded for discharging purposes prior to use. Also in mobile devices in which a fingerprint sensor is provided, the danger remains that the carrying of the device may give rise to an electrostatic charge.
International Patent Disclosure WO 98/52157 teaches a fingerprint sensor in which an electrically conductive layer is disposed beneath a ground plate.
Published, European Patent Application EP 09 02 387 A2 teaches the disposing of a grounded strip-shaped conductive layer longitudinally in the interspaces between conductive plates with the intended purpose of guarding against electrostatic discharges.
It is accordingly an object of the invention to provide an electronic component and the utilization of a guard structure contained therein which overcomes the above-mentioned disadvantages of the prior art devices and methods of this general type, in which reliable ESD protection is provided even when a substantial part is not surrounded by a housing.
With the foregoing and other objects in view there is provided, in accordance with the invention, an electronic component. The electronic component contains a substrate, a dielectric layer disposed above the substrate, conductive surfaces disposed on the dielectric layer, and an electrically conductive guard structure disposed in a plane above the conductive surfaces such that the conductive surfaces are not completely covered by the guard structure. The guard structure is disposed along an interspace region between the conductive surfaces, the guard structure extends in a manner of a strip oblique to a direction in which the interspace region extends.
Providing an electrically conductive guard structure which is disposed in a plane above conductive surfaces and which leaves the conductive surfaces exposed guarantees that the conductive guard structure has the effect of a Faraday cage, given suitable connecting thereof. This is an easy way to guarantee protection against electrostatic discharge.
By virtue of the provided interspace region, the conductive surfaces are not covered by the guard structure. The strip-shaped, angled construction of the guard structure results in non-planar ends which are directed toward the interspace regions and which have the effect of a lightning conductor. The utilization of tungsten to produce the guard structure gives it a high durability.
The guard layer is particularly easy to handle if it is constructed with a width of from 1 to 5 um. Furthermore, the construction of a grate-type guard layer unites easy producibility with high effectiveness as an ESD protection, given minimal material requirements.
In accordance with an added feature of the invention, in a margin of the interspace region, the guard structure changes its direction of progress so as not to exit the interspace region.
In accordance with an additional feature of the invention, the guard structure is constructed from tungsten.
In accordance with another feature of the invention, the guard structure is constructed as a lattice shaped structure.
In accordance with a further feature of the invention, the conductive surfaces form part of an individual sensor element.
In accordance with another added feature of the invention, in a margin of the interspace region, the guard structure changes.
With the foregoing and other objects in view there is provided, in accordance with the invention, a combination of an electronic component having a substrate, a dielectric layer disposed above the substrate and conductive surfaces disposed on the dielectric layer, with a guard device for the electronic component. The guard device contains an electrically conductive guard structure disposed in a plane above the conductive surfaces such that the conductive surfaces are not completely covered by the guard structure. The guard structure is disposed along an interspace region between the conductive surfaces. The guard structure extends in a manner of a strip oblique to a direction in which the interspace region extends, and the guard structure guards against electrostatic discharge.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an electronic component and utilization of a guard structure contained therein, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.